Polsak enjoys the moment after winning Thailand's first women's gold

Udomporn claimed victory in the 53kg class, with Indonesia's Raema Lisa Rumbewas taking silver and Mabel Mosquera of Colombia grabbing bronze.

The Thai lifted 97.5kg in the snatch and 125kg in the clean and jerk for a total of 222.5kg.

"I'm glad to be the first to get the gold medal," said Udomporn.

She added: "I've been training more than 14 years and I've had tremendous support."

A refereeing blunder robbed Polsak of what she thought was an Olympic record.

Udomporn lifted 125.5kg in her final effort in the clean and jerk to top the record of 125kg China's Yang Xia set at the 2000 Sydney Games.

News of the record was broadcast but an International Weightlifting Federation official admitted "it was a big mistake".

"She should not have been allowed to lift that weight," he added, explaining that Olympic records must be beaten by a margin of at least 2.5kgs to be recorded.

To have set a valid record Udomporn would have had to have lifted 127.5kg in her final hoist.

The confusing rule caught out the officials after the Thai coaches called on Udomporn to go for the record after she had already secured victory in the 53kg division with an earlier lift.

Rumbewas ended with a total of 210.5kg, while Mosquera reached 197.5kg.